1. Field of the Invention
This invention relates to a sheet-material discharging mechanism in an image forming apparatus for forming an image on a sheet material.
2. Description of the Related Art
Each of conventional image forming apparatuses for performing recording on a sheet material includes a discharging mechanism for discharging the sheet material after the recording to the outside of the apparatus.
FIG. 6 is a diagram illustrating the configuration of such a conventional discharging mechanism.
The mechanism shown in FIG. 6 relates to an ink-jet recording apparatus. In FIG. 6, a sheet material 4 is fed from a sheet feeding device 3 to sheet conveying rollers 6 and 7 by a sheet feeding roller 5. An image is formed on the sheet material 4 by a recording head 1, and the sheet material 4 having the image thereon is fed to a portion between a sheet discharging roller 10 and a spur roller 11.
Since the spur roller 11 has the shape of a spur, it has the function of discharging the sheet material 4 to the outside of the apparatus while pressing it against the sheet discharging roller 10 without disturbing the recorded image even if the spur roller 11 rubs the image in a state of rotatably contacting the image.
The spur roller 11 is disposed with an angle .alpha. with respect to the sheet discharging roller 10 so that the leading edge of the sheet material 4 is slightly raised when the sheet material 4 is discharged. It is thereby possible to press the sheet material 4 against the surface of a platen 8 in order to maintain the distance between the sheet material 4 and the recording head 1 constant. Furthermore, It is possible to increase the time period from discharge to landing of the sheet material 4 in order to sufficiently dry ink on the preceding sheet material 4.
The discharged sheet material 4 is mounted on a discharged-sheet tray 17 provided outside the apparatus.
When the surface of the discharged sheet material 4 is very smooth, the following problems arise. For example, a discharged sheet of the sheet material 4 slides over the previously mounted sheet to a position beyond a predetermined position, thereby disturbing mounting of sheets of the sheet material 4. If recording is performed on a desk, a discharged sheet of the sheet material 4 drops onto the floor passing through the discharged-sheet tray 17, so that the recorded image on the sheet is stained.
Conventionally, in order to solve the above-described problems, when discharging the sheet material 4 having a recorded image thereon by the sheet discharging roller 10, the speed of discharge of the sheet material 4 is reduced by reducing the rotational speed of the sheet discharging roller 10 or stopping the rotation of the sheet discharging roller 10 immediately after discharge of the sheet in order to prevent the sheet material 4 from passing through the discharged-sheet tray 17 to the outside of the apparatus and thereby to improve the mountability of the sheet material 4. In such a case, however, a case in which the trailing edge of the sheet material 4 remains on the sheet discharging roller 10 may arise. If an operation of inverting the direction of rotation of the sheet discharging roller 10 is performed (which may arise in an initial operation when starting sheet feeding), the sheet material 4 may be drawn backward to cause a jam.